On building and construction sites and in factories, line generators using light sources such as laser diodes, light emitting diodes, and optical fibers are used for setting fiducial lines for positioning, step height measurement and detection of defects.
FIG. 27 and FIG. 28 illustrate an example of configurations of conventional line generators. The line generator includes a laser diode light source 1101, a collimating lens having rotation symmetry 1103 and a rod lens 1105. FIG. 27 shows a cross sectional view in the vertical direction (fast-axis (FA) direction) of the laser diode light source 1101 while FIG. 28 shows a cross sectional view in the horizontal direction (slow-axis (SA) direction) of the laser diode light source 1101. In FIG. 28, light emitted by the laser diode light source 1101 is collimated by the collimating lens having rotation symmetry 1103 in the SA direction to generate a light beam having a width of 3 millimeters. The width of the light beam after the collimation is that of the line generated by the line generator. On the other hand, as shown in FIG. 27, the light emitted by the laser diode light source 1101 is collimated by the collimating lens having rotation symmetry 1103 in the FA direction to generate a light beam having a width of approximately 6 millimeters. After being collimated by the collimating lens having rotation symmetry 1103, the light is diverged in the FA direction by the rod lens 1105 to generate the line.
Since the size of the collimating lens 1103 is limited, only a part of the light which has become approximately 10 millimeter wide in the FA direction is utilized. As a result, maximum light utilizing efficiency is approximately 60%. Further, although a wide diverging angle can be easily obtained, brightness along the line cannot be controlled.
FIG. 29 and FIG. 30 illustrate another example of configurations of conventional line generators. The line generator includes a laser diode light source 1201, a collimating lens having rotation symmetry 1203 and a cylindrical lens 1205. FIG. 29 shows a cross sectional view in the vertical direction (fast-axis (FA) direction) of the laser diode light source 1201 while FIG. 30 shows a cross sectional view in the horizontal direction (slow-axis (SA) direction) of the laser diode light source 1201. In FIG. 30, light emitted by the laser diode light source 1201 is collimated by the collimating lens having rotation symmetry 1203 in the SA direction to generate a light beam having a width of 3 millimeters. The width of the light beam after the collimation is that of the line generated by the line generator. On the other hand, as shown in FIG. 29, the light emitted by the laser diode light source 1201 is collimated by the collimating lens having rotation symmetry 1203 in the FA direction to generate a light beam having a width of approximately 6 millimeters. After being collimated by the collimating lens having rotation symmetry 1203, the light is diverged in the FA direction by the cylindrical lens 1205 to generate the line.
Since the size of the collimating lens 1203 is limited, only a part of the light which has become approximately 10 millimeter wide in the FA direction is used. As a result, maximum light utilizing efficiency is approximately 60%. Brightness along the line can be arbitrarily controlled by adjusting a shape of the optical surface of the cylindrical lens 1205. However, due to restriction in manufacturing a mold used for molding the lens, a tangential angle of the cylindrical shape can hardly be enlarged, and therefore a wide diverging angle can hardly be obtained. Further, the light beam is designed to be focused at a position of a certain distance such that brightness along the line is made uniform. Accordingly, when the collimating lens 1203 is adjusted for focusing, brightness along the line will deviate from the designed value.
Japanese patent application laid open No. 2008-58295 discloses one of conventional line generators. U.S. Pat. No. 6,069,748 discloses another one of line generators.
Thus, a line generator having high light utilizing efficiency in which a wide diverging angle is obtained and brightness along the line can be easily controlled has not been developed.
So, there is a need for a line generator having high light utilizing efficiency in which a wide diverging angle is obtained and brightness along the line can be easily controlled.